Diameter Calculator - Find Diameter from Radius Formula
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Diameter Calculator

Find circle diameter from radius

Diameter Formula

d = 2r

The diameter is the full width of a circle through its center. Since the radius is half that distance, multiplying the radius by 2 gives the diameter.

⚠This calculator uses radius as the input. Radius must be zero or positive.

How Diameter Works

Diameter is the longest chord of a circle and always passes through the center. It is exactly twice the radius.

Radius

Half the diameter.

Center Line

Diameter passes through the center.

Longest Chord

No circle chord is longer.

Scale

Doubling radius doubles diameter.

💡 Example: If r=6, d=2(6)=12.

Applications of Diameter

Pipe SizeWheel SizeCircle DrawingManufacturing

Frequently Asked Questions

What is a diameter calculator?▼
It calculates the diameter of a circle from its radius.
What is the diameter formula?▼
The formula is d=2r, where r is the radius.
How do I use this calculator?▼
Enter the radius value and click Calculate.
Can diameter be zero?▼
Yes. If radius is zero, diameter is also zero.
Where is diameter used?▼
Diameter is used in circle measurements, pipes, wheels, holes, and round objects.

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